SAGINAW — When it comes to dioxin contamination, where you live may not matter as much as what you eat.

Midland and Saginaw County residents should be cautious about eating certain fish, meat and animal products from the area where historic releases of dioxin have tainted the soil, said Dr. David Garabrant, leader of a University of Michigan Dioxin Exposure Study. Combustion or other industrial processes create dioxins, some of which have links to cancer in lab animals.

Thursday, U-M released a final update on its six-year study, which tested dioxin levels in soil, household dust and blood samples from residents in the Tittabawassee River floodplain from the Dow Chemical Co. plant in Midland through Midland and Saginaw counties. The study did not test the effects of dioxins on the health of residents.

The study found ingesting meat and products such as eggs and milk from animals raised in dioxin-contaminated areas increases the level of the chemicals in people’s blood.

“Food matters,” Garabrant said.

Dow gave U-M an unrestricted grant to conduct the study, an aspect that has drawn environmentalists’ criticism. The university controlled all aspects of the study, and Dow had no influence on the results, Garabrant said.

Bay City-based environmental group the Lone Tree Council member Michelle Hurd-Riddick was reviewing the report and did not have immediate comment on its contents.

Tittabawassee-Saginaw Rivers Contamination Community Advisory Group member Judith A. Lincoln said the group plans to look over all information regarding dioxin, but she could not say whether the U-M study will have an impact on the group’s recommendations to the U.S. Environmental Protection Agency and Michigan Department of Natural Resources and Environment for the cleanup.

U-M researchers tested blood samples from 695 Midland and Saginaw county adults and 251 Jackson and Calhoun county adults from 2003 to 2006.

Dioxins in the environment that get into the food chain increase blood-dioxin levels, Garabrant said, but he does not believe most dioxins are getting into the food chain. One participant in the study who raised and ate cattle in the floodplain had elevated levels of dioxins. However, Garabrant said, few residents reported eating animals raised in the area. Local animals can ingest the chemicals by eating contaminated soil.

Residents should follow Michigan Department of Community Health guidelines when it comes to eating fish and game, Garabrant said, and they should not eat eggs or milk from animals in the floodplain.

Age remains the top reason for increased dioxins in a person’s bloodstream, Garabrant said, because older people were alive when the U.S. had higher levels of dioxins, they have eaten more contaminated meat and fish in the course of their lifetimes and older people expel dioxins from their system more slowly than younger people.

Adults 30 and younger who were raised in the floodplain do not have higher levels of dioxins than the national average, the study showed.

The latest and final chapter in the study contradicted preliminary results released in 2006 in four areas:

• There is no correlation between eating fish from the rivers and having higher levels of dioxin in the blood. The 2006 results suggested eating fish increased dioxin levels.

Garabrant said the new study includes Michigan State University data about animals in the region. The researchers found most people eat local fish such as walleye, which is not contaminated, instead of bottom feeders such as carp and catfish, which are contaminated.

• People who lived in the floodplain prior to 1980 have higher levels of dioxin in their bodies than those who lived in the area after 1980. The study states airborne emissions during the 1960s and ’70s are likely the reasons for the higher levels. The 2006 study showed people who lived in the area between 1940 and 1959 had higher levels of dioxins. Further study indicated 1960s and ’70s residents also have higher levels of the chemicals in their bodies.

Garabrant said additional dioxin contributions from Dow halted, and dioxins have since dissipated or are locked into the soil and are unavailable to fish, animals and humans.

• Floodplain residents who live on contaminated soil and have contaminated dust in their homes do not have higher levels of dioxins in their blood. The 2006 results showed residents who have higher levels of dioxin in their soil had higher levels of some of the chemicals in their blood. The reason for the discrepancy was a single soil sample that was high in one chemical at one address, the study stated.

• The reason Saginaw and Midland county residents have a higher level of dioxins in their blood than Jackson and Calhoun county residents related to the time period in which they lived here rather than location.

Dioxins are chemicals that leaked from the Dow plant into the Tittabawassee River and into the air from the 1930 to the 1970s. The chemicals are linked to cancer, reproductive problems and weakened immune systems in laboratory animals.

The study also found:

• There is no relationship between eating fruits and vegetables and higher dioxin blood levels, but residents with gardens in contaminated areas should be careful not to ingest soil.

“Wash your fruits and vegetables carefully,” Garabrant said.

• The study showed Dow employees have higher levels of some dioxin chemicals in their blood.

• Women tend to have higher levels than men.

Garabrant said people and agencies involved in the cleanup process should consider the results of the study.

“The real value of the study is that it gives everyone facts to go on,” he said.

The full report is available online and in public libraries in Midland and Saginaw counties and Auburn.